Yun Hee-jung (윤희정), also romanized Yoon Hee-jung, Yun Hui-jeong and Youn Hee-jung, is a South Korean jazz vocalist whom the press calls the godmother of Korean jazz (한국재즈 대모). She was born Kim Myeong-hee (김명희) on June 11, 1953, in Songhyeon-dong, Dong-gu, Incheon, the second of six children of a father from Pyeongan Province and a mother from Suncheon, according to the Kyeongin Ilbo (2023), the Melon and Kyobo artist pages and the critic Park Seong-seo. Some press ages printed in 2004 would put her birth a year or two later, but every source that gives a date says 1953.

She grew up singing. She led the music club at Inseong Middle and High School in Incheon, learned guitar in the Incheon YMCA's Singalong group, and in 1971, just out of school, won the first KBS national singing contest (전국노래자랑) with "Senoya", a song with words by the poet Ko Un. KBS kept her on a salary as an exclusive singer for about two years. Her debut LP, a folk record that opens with her own "Naenim-ui moksori", came out in April 1972, and a second followed that year. Her older brother, a judge, chose the stage name Yoon Hee-jung to help her stand out.

After marriage and children she turned to gospel and sang at missions in the United States and Europe. Jazz came late. She first met it in 1991, according to the Hankook Ilbo, and began studying in 1992 with Lee Pan-geun (이판근), the theorist often called the godfather of Korean jazz. The Kyeongin Ilbo says a management company had suggested she try jazz and that Lee first tried to dissuade her. Her first jazz album appeared in 1994, according to the Hankook Ilbo and the Kyobo biography; Korean streaming catalogues date its digital edition February 1995. It is nine standards, opening with "I'm a Fool to Want You".

In June 1997 she began Yoon Hee-jung & Friends, monthly concerts at the Jeongdong Theater in Seoul in which she coached well-known people from outside music, among them actors, politicians and a film director, before they sang jazz beside her. It later moved to the Munhwa Ilbo Hall, passed its hundredth show and ran until 2011, and each guest trained for two to three months. The Hankook Ilbo counted more than 130 guests by May 2004; the Kyeongin Ilbo later gave about 200 students and the Korea Herald about 250 guests. Names in the press include Kim Gun-mo, Lee So-ra, Lee Mi-sook, Song Il-kook, Park Kyung-lim and Ok Joo-hyun. Since 2013 she has run Jazz Friends Party, with amateur singers on stage, and since 2000 a December concert series has used venues from the Walker Hill Hotel to the Westin Josun Seoul to Raum in Seoul.

C.E.O.J Vol. 1 (April 23, 2004) was her first jazz album with wide distribution, issued through Sony Music with the agency JMA. The title abbreviates "Co-Edutainment of Jazz", and she said she meant it as the first of a series. The cover credits the saxophonist Lee Jung-sik, Lee Dong-ki and Kim Soo-yeol, and the Hankook Ilbo says Lee Pan-geun set her words about her parents' home towns to music as "Y.H.J Blues". A third jazz-leaning album, Yoon Hee-jung's Love, followed in 2010. In 2017 the Mnet competition The Master cast her as its jazz master; she sang "Senoya", Kim Gun-mo's "Seoul-ui Dal" in a jazz arrangement and, with her daughter, "Spain". Her daughter Kim Su-yeon (김수연), who performs as Somerz (쏘머즈), accompanies her at each December concert. She was still working in 2026: the Arirang Radio program Peters on the Block interviewed her in July.

Her repertoire is the American standard book: "You'd Be So Nice to Come Home To", "All or Nothing at All", "My Heart Belongs to Daddy", "Put the Blame on Mame", "What a Wonderful World" and "Bei Mir Bist Du Schon", which she performed live on Arirang Radio in 2025. The 2004 album opens with "You Don't Know What Love Is" and includes "Afro Blue", and the Korea JoongAng Daily noted that it moves from well-known standards toward more complex pieces. In 1972 the producer of the KBS contest, Oh Yong-hwan, was quoted comparing her voice to Mahalia Jackson's.

The Korean side is deliberate. She told the Hankook Ilbo that after noticing American interest in Indian-influenced jazz she wanted a "third rhythm" of her own, mixing Latin, African and samulnori rhythms, and she explained the kkwaenggwari, the small gong, that she holds on the cover of C.E.O.J as part of that idea. "Y.H.J Blues" sets her lyrics against Lee Jung-sik's saxophone, a taepyeongso (Korean shawm) and the gong. The same album takes in "Senoya" and the traditional folk song "Bunkkot", the Melon album note mentions Korean lyrics and a rap feature, and the JoongAng Daily described a blues that blends Korean rhythms with Latin instruments.

She treats jazz as something to share. She says jazz is about compassion rather than passion, that it taught her to aim to be the only one rather than the number one, and that she makes music that is easy to listen to. Not all of her later records are jazz: a 2015 second album re-records her folk songs, trot and disco collections followed in 2018 and a trot cover EP in 2024, and the Korea Herald reported in 2023 that she planned an album of reimagined trot and pop songs.